HE'S TOTALLY RIPPED

My, how you've grown! To prepare for his role as a marine in The Lucky One, Zac Efron packed on 18 lbs. of muscle and showed off his new six-pack during a workout at L.A.'s Manhattan Beach last year. "He loves being outdoors, hiking and exercising outside," a source told PEOPLE of the 24-year-old star. "He's always been in shape."